lib/dma-debug.c: mark file-local struct symbol static.

warning: symbol 'filter_fops' was not declared. Should it be static?
Signed-off-by: Thiago Farina <tfransosi@gmail.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

lib/dma-debug.c

@@ -587,7 +587,7 @@ out_unlock:
 	return count;
 }
 
-const struct file_operations filter_fops = {
+static const struct file_operations filter_fops = {
 	.read  = filter_read,
 	.write = filter_write,
 };